Isolation of Bacteria Growing on Different Tissues of Flathead Grey Mullet (Mugil cephalus) Collected from Sousa Port

Abstract

This study investigated the microbial contamination of flathead grey mullet (Mugil cephalus) collected from Sousa fishing port, with a focus on the presence of pathogenic and indicator bacteria. A total of ten fish samples were randomly collected and subjected to morphometric analysis, bacteriological examination, and water quality assessment. Bacterial isolation was performed using selective and differential culture media, followed by identification based on morphological and biochemical characteristics. The results revealed that all examined fish samples were contaminated with bacteria, indicating widespread environmental pollution. The most prevalent bacterial species were Klebsiella spp. (60%), followed by Salmonella enterica (50%) and Escherichia coli (40%). Tissue-specific analysis showed that the gills exhibited the highest level of contamination, while the stomach showed the lowest, suggesting that direct exposure to polluted water plays a major role in microbial colonization. Additionally, growth patterns on culture media confirmed the presence of enteric and potentially pathogenic bacteria. Water quality parameters, including pH, total dissolved solids (TDS), and electrical conductivity (EC), showed relatively stable values between sampling sites, indicating that microbial contamination was primarily associated with pollution sources rather than environmental variation. In conclusion, the findings of this study highlight the significant impact of sewage discharge on fish contamination and emphasize the potential public health risks associated with the consumption of contaminated seafood. The study underscores the need for effective wastewater treatment, continuous environmental monitoring, and strict food safety regulations to ensure the safety and quality of marine resources.